Technical Field
The present invention relates to flash memory, and in particular to methods for maintaining a storage mapping table and apparatuses using the same.
Description of the Related Art
Flash memory devices typically include NOR flash devices and NAND flash devices. NOR flash devices are random access—a host accessing a NOR flash device can provide the device any address on its address pins and immediately retrieve data stored in that address on the device's data pins. NAND flash devices, on the other hand, are not random access but serial access. It is not possible for NOR to access any random address in the way described above. Instead, the host has to write into the device a sequence of bytes which identifies both the type of command requested (e.g. read, write, erase, etc.) and the address to be used for that command. The address identifies a page (the smallest chunk of flash memory that can be written in a single operation) or a block (the smallest chunk of flash memory that can be erased in a single operation), and not a single byte or word. In practice, to improve the write speed, data of continuous logic addresses may be dispersed into physical storage units, and a storage mapping table is used to point to where the data is written in physical storage units. Accordingly, what is needed are methods for maintaining a storage mapping table to improve the rebuild speed, and apparatuses that use these methods.